Cyclic guanosine monophosphate (cGMP) is known to be an important physiological mediator of vasorelaxation. A major process in vascular smooth muscle contraction is hydrolysis of cGMP by calcium-calmodulin dependent phosphodiesterase (Ca CaM PDE). Since Ca CaM PDE is selective for cGMP, selective inhibition of this enzyme should elevate cGMP levels in vascular smooth muscle and induce vasorelaxation.
Griseolic acid, disclosed in U.S. Pat. No. 4,460,765, is a nucleoside-type compound having an adenine base and a bicyclic sugar moiety and has a structure similar to adenosine 3',5'-cyclic monophosphate (cAMP). cAMP is known to be a mediator of a large number of hormones and griseolic acid similarly appears to inhibit a large variety of phosphodiesterases (PDEs).